Process for separating plutonium by repeated precipitation with amphoteric hydroxide carriers



Aprnl 5, 1960 B. F. FARIS 2,931,701

PROCESS FOR SEPARATING PLUTONIUM BY REPEATED PRECIPITATION WITH AMPHOTERIC HYDROXIDE CARRIERS Filed Sept. 2, 1944 So/ut ion Containiny Pu I 1 I I Phosphate 12 I Precipitation I I I l I Waste Preeioitate I I iauor I Containing Pu I I I Phosphate I (Oxidation) 3 I Pree/pizafion I I I I Waste Solution Containing I I precipitate Oxidized Pu I lnoorpor'azion of a Source of lane of at Least One or. the Meta/s -6 Al, Bi, Cu, (0, Fe, La, Ni, Zr

Ma/re Solution Alkaline 6 Pea'iseo/ve Preeq'oitaz 7 Re reci itate Hydroxide a: at teast One of I15 the above Meta/s I Waste Hydroxide Prec/pitate I LAW/0r I m 9 PM I I I 1 Waste Hydroxide Pree/pitate I Liquor I Carrying Pu I F Pad/350m recipitate I and Further' Treat to 9 Concentrate or Separate Pu I BY I We M United States Patent PROCESS FOR SEPARATING PLUTONIUM BY REPEATED PRECIPITATION WITH AMPHO- TERIC HYDROXIDE CARRIERS Burt F. Faris, Oak Ridge, Tenn., assignor to the United States of America as represented by the United States Atomic Energy Commission Application September 2, 1944, Serial No. 552,547

16 Claims. (Cl. 23-145) This invention relates to a method for processing materials containing the element of atomic number 94, known as plutonium, and specifically to a method for separating the plutonium from extraneous matter associated therewith particularly substances of the kind present in neutron irradiated uranium such as uranium, fission products, and the like. More particularly, this invention concerns a separatory and concentration procedure involving the use of hydroxide carriers, and especially processes employing two or more metallic hydroxide carriers As described herein, the isotope of element 94 having a mass of 239 is referred to as 94 and is also called plutonium, symbol Pu. In addition, the isotope of element 93 having a mass of 239 is referred to as 93 Reference herein to any of the elements is to be understood as denoting the element generically, whether in its free state or in the form of a compound, unless indicated otherwise by the context.

Elements 93 and 94 may be obtained from uranium by various processes which do not form a part of the present invention including irradiation of uranium with neutrons. Neutron irradiated uranium may be prepared by reacting uranium with neutrons from any suitable neutron source, but preferably the neutrons used are obtained from a chain reaction of neutrons with uranium.

Naturally occurring uranium contains a major portion of U a minor portion of U and small amounts of other substances such as UX and UX When a mass of such uranium is subjected to neutron irradiation, particularly with neutrons of resonance or thermal energies, U by capture of a neutron becomes U which has a half life of about 23 minutes and by beta decay becomes 93 The 93 has a half life of about 2.3 days and by beta decay becomes 94 Thus, neutron irradiated uranium contains both 93 and 94 but by storing such irradiated uranium for a suitable period of time, the 93 is converted almost entirely to 94 In addition to the above-mentioned reaction, the reaction of neutrons with fissionable nuclei such as the nucleus of U results in the production of a large number of radioactive fission products. At it is undesirable to produce a large concentration of these fission products which must, in view of their high radioactivitity, be separated from the 94 and further as the weight of radioactive fission products present in neutron irradiated uranium is proportional to the amounts of 93 and 94 formed therein, it is preferable to discontinue the irradiation of the uranium by neutrons when the combined amount of 93 and 94 is equal to approximately 0.02 percent by weight of the uranium mass. At this concentration of these substances, the concentration of fission elements which must be removed is approximately the same percentage.

A number of processes have already been proposed for accomplishing the aforementioned separation and concentration of plutonium. Certain of these processes are known generically as the dry processes and wet processes. For example, certain of the wet processes have involved ice the use of various types of carriers for carrying the product out of solution, alternate reduction and oxidation steps, and a number of other chemical steps. Such processes have been conducted under acidic conditions, and have involved the use of reagents such as hydrogen fluoride. More specifically, certain of these processes are known as the bismuth phosphate process and lanthanum fluoride process. In some of the steps of these prior processes a special technique known as metathesis as hereinafter described, has been required for redissolving the carrier precipitate containing product. Also relatively large amounts of carrier precipitate and liquids are required to be handled in carrying out the prior processes. The meaning of the various items referred to above such as carrier precipitate, the use of fluorides and other items will be apparent as the description proceeds.

I have found a new method for accomplishing the aforementioned separation and concentration of plutonium wherein different types of reagents may be used and advantages obtained, not only in being able to accomplish separation by an alternative manner, but in which reduction of carrier bulk and other advantages may be obtained.

This invention has for one object, to provide a new method for the separation and recovery of plutonium.

Another object is to provide a method of separating plutonium by a carrier procedure wherein difierent types of carriers than have heretofore been used may be employed.

Still another object is to provide a separatory and concentration process which may be operated under alkaline conditions as contrasted with acidic conditions employed in many of the processes heretofore practiced.

A still further object is to provide a process for separating Pu wherein substantial reduction of carrier'bulk and extraneous materials may be accomplished.

Still another object is to provide a novel process for separating Pu which lends itself to coupling or adaptation with processes already known or practiced.

Another object is to provide a novel separatory process for the recovery of Pu which may be carried out in existing equipment without change, or with a minimum of equipment change.

Still another object is to provide a process of the type described employing amphoteric metal hydroxide carriers.

Another object is to provide a crossover process for the separation and concentration of Pu.

Still another object is to provide a process for the recovery of Pu which may be applied to Pu containing solutions either in the reduced or oxidized state.

Another object is to provide a separatory and concentration process for Pu containing materials involving the use of one or more metal hydroxide carriers.

Other objects will appear hereinafter.

For a better understanding of the invention, reference is made to the attached drawing forming a part of the present application. In this drawing, a diagrammatic representation of one embodiment of the invention is given in the form of a flow sheet.

I have found that plutonium in admixture with extraneous material may be separated and concentrated by the use of metal hydroxide carriers. That is, the present process is directed in certain phases to the use of various metal hydroxide carriers for Pu, and particularly to the use of these carriers in a series of steps where a preliminary d'econtamination process, as a bismuth phosphate process, has been employed for the initial treatment of the materials from which the Pu is being separated. It has been found that by such a procedure, the addition of large amounts of carrier may be avoided, and that carrier bulk and liquid volumes may be progressively reduced.

While, as indicated,it is preferred to employ my process in conjunction with the bismuth phosphate process, it is to be noted that my process may also be carried out independently thereof.

The bismuth phosphate process is set forth in app. Ser. No. 517,719, filed January 26, 1944, Thompson and Seaborg, now Patent No. 2,785,951, issued March 19, 1957, and reference is made to that application for full disclosure of that process, details thereof being omitted from the present disclosure except where necessary to an understanding of the present invention. As set forth in said application, it has been discovered that plutonium has more than one oxidation state, including a lower oxidation state or states referred to herein as Pu in which the element is characterized by forming insoluble phosphates and fluorides and a higher oxidation state or states referred to as Pu in which the element forms soluble phosphates and fluorides. As noted above, it is a feature of the present invention that plutonium may be carried by an amphoteric hydroxide particularly under alkaline conditions in either oxidation state.

In general, my separatory and concentration procedure for recovering plutonium is as follows: A quantity of processed uranium (neutron bombarded) is obtained. The particular source is not a limitation on my invention. In the operation of the invention the processed U is, of course, properly handled as respects aging or other treat ment so that there is present therein the desired plutonium in a suitable condition to be separated and concentrated. The uranium is dissolved in a suitable solvent. For example, nitric acid may be used in this step for obtaining a uranium nitrate hexahydrate solution. The uranyl nitrate hexahydrate solution is suitably reduced and preferably subjected to an extraction and decontamination procedure. This procedure may comprise treatment by the bismuth phosphate method as described in the aforementioned app. Ser. No. 519,714 under alternate reducing and oxidizing conditions. By such a procedure, by-products are eliminated to a substantial extent. For example, the product Pu is isolated from at least a part of the uranyl nitrate hexahydrate and fission products or other contaminants, and extraneous matter. At some suitable stage when decontamination has been carried to a satisfactory point, and at a stage when oxidizing conditions prevail, a bismuth phosphate by-product precipitate is taken and the filtrate or centrifugate, depending upon the method of physical separation used in the process, is segregated as this contains the product Pu in an oxidized state.

The preceding preliminary treatments or other preliminary treatments may be carried out until the decontamination has been carried to the desired extent. Such preliminary treatments result in solutions containing Pu together with various amounts of extraneous materials in substantial volumes of liquids which lend themselves to treatment by my process.

I have found that aluminum, bismuth, copper, cobalt, iron, lanthanum, nickel, and zirconium in the form of their hydroxides are excellent carriers for plutonium.

The procedure is preferably applied to the solution of product in approximately 1 M nitric acid. After a preliminary treatment of the type above indicated, such as the removal of at least one bismuth phosphate by-product precipitate, a soluble salt of the carrier metal is added to make the concentration in the solution being treated of from about 50-500 mgs. per liter. The solution is then made neutral or slightly alkaline by the addition of a source of hydroxide ion. Or if desired, a pre-formed hydroxide precipitate may be made and the slurry added. While the use of metal hydroxide carriers in accordance with the present invention is described in particular as applied to a reduced solution-containing product, this is optional as all of the metal hydroxides described herein, as will be indicated hereinafter, have been found to carry both oxidized and reduced Pu substantially equally well.

After treatment of the solution to form the insoluble metal hydroxide carrier or carriers therein, $1 9 99 precipitate with the plutonium is centrifuged or otherwise separated from the mother liquor and then redissolved. The factor of volume reduction achieved in my process is of the order of 300 or greater.

In the examples which follow, the U was dissolved in a suitable solvent and the resultant solution subjected to a bismuth phosphate process as described in app. Ser. No. 519,714, now Patent No. 2,785,951, issued March 19, 1957, aforementioned, filed January 26, 1944, Thompson and Seaborg. That process removed most of the uranium and some of the fission products. Other treatments producing equivalent results and yielding a suitable solution for the practice of this invention may be employed in lieu of the method suggested. The solution was then processed in accordance with the method of the present invention.

For a general understanding of the process, reference is made to the attached drawing. The solution containing Pu to be treated is indicated at 1. In cycle A, the preliminary treatment for removing uranium and fission products is applied. That is, several phosphate precipitations, as indicated at 2 and 3 may be applied until the desired decontamination is accomplished.

In cycle B which will be described in detail hereinafter, a preliminary reduction step may be employed. A source of one or more of the ions of the metals aluminum, bismuth, copper, cobalt, iron, lanthanum, nickel, and zirconium is added. Also a source of hydroxide ions is added and other steps for forming a hydroxide precipitate, as indicated at 5 and 6, are accomplished. The precipitate is then redissolved in step 7 and another hydroxide precipitation accomplished as indicated at 8.

This cycle may be repeated several times.

In cycle C, it is generally indicated at 9 that further treatment as is desired, may be applied.

EXAMPLE I Considering now the steps pertaining in particular to this invention, it has been found that carriers formed from elements such as aluminum, bismuth, cobalt, nickel, copper, chromium, lanthanum, iron, and zirconium reacted with a suitable source of hydroxide ions will carry product in either the (0) or (r) state. The solution from the preceding preliminary treatment was reduced with hydrogen peroxide. However, as indicated, the reduction step is optional.

Also, this solution containing Pu is preferably treated by adding slightly less than the calculated amount of sodium ferrocyanide to react with any iron present. This is done after the separation of a phosphate (oxidation) precipitate, and the resulting iron containing precipitate separated.

It has been found that although the Pu is probably in the reduced state the compound formed from the aforementioned addition does not carry the Pu. It is thought that the added compounds, as for example, Na Fe(CN) reduces Pu and in addition reacts with ferric ions present to give Fe [Fe(CN) The latter compound does not appear to carry the Pu even though the Pu is in a reduced state. The potassium salt may be used in place of the sodium ferrocyanide.

This solution may be treated with .05.l gram per liter of oxalic acid, citric acid, or other compound having comparable complexing properties. The solution may contain other metal ions than the particular ion from which it is desired to form the hydroxide carrier precipitate, such as bismuth from a prior bismuth phosphate precipitation step, or iron, if a ferrous material has been used as a reducing agent in preceding steps. The addition of the complexing agents is for the purpose of eliminating other metal ions so that the carrier formation will result substantially exclusively from the addition of the particular metal such as aluminum, cobalt, and copper.

For the purpose of this application Zr and Fe are broadly referred t herein. as amphoteric although these .'which may be optional.

metal hydroxides are not soluble in alkali in a manner comparable to the other metal hydroxides.

After the aforementioned .complexing or equivalent treatment, the amphoteric element was added. A small amount, as for example, between 25 milligrams to 250 milligrams per liter was added in this example. The element was added in the form of the soluble salt, aluminum nitrate. However, various other derivatives as exemplified by sulfate and acetate may be employed.

The solution from this step had a content of aluminum ion therein. The solution was treated with sodium hydroxide. However, potassium hydroxide, or ammonium hydroxide as a source of hydroxide ions for reacting with the metal ions to form a metal hydroxide carrier precipitate may be used. The alkali addition was sutficient to render the solution alkaline to litmus. Preferably a pH of 8 or greater is attained. The reaction time at a temperature from room temperature to 100 C. (about 75 C. being preferred) was from one-half to two hours. The additions and reaction were accompanied by slow sweep agitation. The resultant precipitate of aluminum hydroxide carrying plutonium was centrifuged, and the centrifugate discarded to waste. The separated precipifate was washed. Dilute alkali solutions and water were used to wash the hydroxide precipitate.

This precipitate of aluminum hydroxide carrying product was then redissolved in sodium hydroxide, in accordance with the following reaction:

The solution resulting from the redissolution in the preceding step was then treated with a source of another amphoteric element from the aforementioned group. Since a source of aluminum ion was added in forming the aforementioned precipitate, copper was added to the solution resulting from dissolving this precipitate in the form of copper nitrate in the amount of between 25 milligrams and 250 milligrams per liter. The other conditions for precipitating hydroxide carrier were the same as in the preceding step.

This precipitated copper hydroxide, Cu(OH) which carried the Pu. A volume reduction in carrier was obtained inasmuch as the amount of copper nitrate added for obtaining this precipitate was substantially smaller than the corresponding amount of metal ion required in preceding steps.

The resultant copper hydroxide precipitate carrying Pu was centrifuged. The copper hydroxide precipitate with carried product was dissolved in ammonium hydroxide with which it underwent the well known reaction:

The solution which resulted from dissolving the copper hydroxide precipitate was then treated with aluminum nitrate to form further aluminum hydroxide carrier precipitate which carried down the product from the copper .containing solution.

The preceding cycles may be repeated a number of 'times or the precipitate carrying product may be dis- .-solved in acid and treated by the lanthanum fluoride precipitation cycle or other known procedure. The alumi- :num hydroxide precipitation may be followed by the use of nickel or cobalt rather than copper. These and other :modifications of my process will be apparent from the 'further examples.

In the preceding example, steps have been described Certain of the steps have been "referred to for illustrating types of preliminary procedure 'which may be employed in my process or otherwise used in conjunction therewith. When applying my process to certain plutonium containing materials as uranium re- .acted with neutrons from a chain reaction, because of presence of a number of contaminants, more extensive preliminary treatment may be desirable than when the ,zprocess is applied to plutonium obtained from other sources. Therefore, it is apparent that the extent and type of preliminary treatments applied is to some extent governed by the nature and quantity of the extraneous material which may be in admixture with the plutonium.

The hydroxide precipitates carrying product obtained in preceding steps in accordance with my invention may be placed in solution. The resultant solutions may then be treated as indicated, by standard procedures for further concentrating the product or for preparing Pu derivatives.

As pointed out above, the present invention is particularly directed to the use of amphoteric metal hydroxide carrier precipitates. The use of my process permits volume reductions by factors greater than 300.

In the examples which follow it will be assumed that the plutonium containing material has been given such preliminary treatments as deemed desirable.

EXAMPLE II In accordance with this example, the plutonium containing solution was treated with a source of aluminum ion. That is, aluminum hydroxide was precipitated by adding 0.6 g. Al(NO .9H O per liter of 1 N HNO to a solution containing oxidized plutonium and making the solution barely alkaline. The precipitate which formed was centrifuged 011? and dissolved in sodium hydroxide. To this alkaline solution was added dissolved copper nitrate. The copper hydroxide which formed was digested one hour with stirring, then centrifuged off. The separated copper hydroxide precipitate carrying Pu was redissolved in ammonium hydroxide and a much smaller amount of aluminum salt added to the solution. The product was carried through the aforementioned cycles with essentially quantitative yields.

The preceding example was repeated in the converse, namely, the copper salts were added first and the process worked equally as satisfactory. The above processes, for convenience of designation are referred to as aluminumcopper or copper-aluminum combinations. In a similar manner, other processes such as aluminum-chromium, aluminum-nickel, or aluminum-cobalt combinations may be carried out.

Various other combinations may be carried out as will be apparent from the following solubility data:

Hydroxide Nitric K200 NaOH NH OH Acid Zr(OH)4 soluble insoluble insolnbleinsoluble. La(OH) do soluble .-.do D0. Al(OH)a do insoluble soluble Do. Cu(OH)a o ...do insolub1e soluble.

For example, one concentration method is based on the carrying of product with aluminum hydroxide, dissolving the Al(OH) in excess NaOH, precipitating La(OH) therefrom, dissolving the La(OH) in K CO and again precipitating Al(OH) from the carbonate solution. Other concentration systems in accordance with my invention may be based on the combinations of lanthanum-copper or lanthanum-aluminum. In a similar manner systems employing bismuth hydroxide may be carried out either preceded or followed by the precipitation of other hydroxide carriers of the type described. The utilization of bismuth hydroxide and certain other hydroxides per se, in certain ways as carriers forms the subject matter of related copending applications.

It is also apparent from the preceding description that other elements might be substituted for the ones indicated above provided their chemical behavior and solubilities are satisfactory. When the hydroxides are precipitated from a reduced plutonium solution obtained from a bismuth phosphate cycle, a mixed precipitate of phosphate and hydroxide may be formed. This does not impair the effectiveness of the method, however, since the phosphate is usually soluble in the same agent that solubilizes the hydroxide.

In the preceding example, the use of a plurality of hydroxides and the crossover from one metal hydroxide to another, has been described. The term crossover process as used herein refers to the type of process of changing from one carrier to another. In my process it is also possible to use only a single hydroxide as will be described in the next example.

EXAMPLE III Carrying of plutonium by insoluble hydroxides [All values in counts per minute per gram of UNHJ Carrier Zr(OH)4 La(OH) Al(OH)3 Cu(H)a Initial solution-.- 539 539 539 539 Waste mother liquor 0. 5 2. 4 4. 0 4. 9 Final product 478 562 530 544 "Some product 10st in preliminary by-product precipitation.

In the above table, the carrying of product was determined from the alpha activity. That is, the alpha activity of the solution before precipitation indicates the amount of Pu present. A comparison therewith of the alpha activity of the precipitate indicates the amount of product carried. The product is an alpha emitter whereas byproducts, exemplified by fission products, are beta and gamma emitters. In Example III the count was low indicating that very small amounts of Pu were present, namely, approximately tracer amounts. However, my process functions equally well when larger amounts, as 50 milligrams of product per liter, or greater are present.

My process may be repeated a plurality of times for obtaining concentration and volume reduction after which it may be coupled with the various other types of processes. Inasmuch as these other types of processes per so are not part of the present invention, they are only briefly referred to herein and are not claimed excepting insofar as they combine or couple with the metal hydroxide process of the present invention.

By the term carrying, carrier, or carrier precipitate employed herein is meant the formation and action of precipitate in the removal of the product from solution such as that which takes place when the metal hydroxide precipitate is formed as illustrated by the preceding examples. By the use of the terms metal hydroxide precipitate, it is intended to include the type of precipitate which is formed by the addition of a source of hydroxide ions to solutions of the type described. This precipitate, as has been indicated, may not only comprise the hydroxide of the particular metal added, but may contain other hydroxides or phosphates depending upon the content of other components in the solution which form precipitates. Furthermore, a plurality of hydroxide forming components may be added. The hydroxide carrier precipitates of the present invention may be formed in a number of ways. Rather than adding the source of the metal ion first, the hydroxide ion may be first incorporated, or a pre-formed precipitate may be prepared and added as a slurry.

The process has been described particularly as applied to solutions having a very small amount of metal present as for example tracer amounts, or solutions resulting from dissolving the materials wherein there are only a few grams of Pu in several tons of neutron treated materials. The process may also be applied to a solution resulting from the dissolution of a material containing 200-300 grams of product per ton of material. Therefore, the specific amount of Pu is not a limitation on my invention.

While certain temperatures, concentrations, and conditions have been specifically indicated in the description of my process for disclosing preferred conditions, these conditions may be varied. For example, the temperature of precipitation and digestion may be from 50 C.- C.

The extent of decontamination of solutions or precipitates may be determined in accordance with a known technique such as making counts of the material by means of Geiger-Muller counters or similar apparatus. The particular technique employed in this and certain other control steps is not a limitation upon the present invention. The handling of materials exhibiting radioactivity would be in accordance with the best technique available at the time the process was being carried out.

It is to be understood that all matter contained in the above description and examples shall be interpreted as illustrative and not limitative of the scope of this invention.

I claim:

1. In a process for separating and concentrating plutonium values from an aqueous solution thereof, the multiple carrier precipitation steps which comprise precipitating in said solution a hydroxide of an amphoteric-type metal other than plutonium, separating from the supernatant liquid the consequent metal hydroxide precipitate and the plutonium values resultingly associated therewith, dissolving the separated precipitate to form a second aqueous plutonium-containing solution, precipitating in said second solution a hydroxide of a metal other than plutonium, and separating from the supernatant liquid the consequent metal hydroxide precipitate and the plutonium values resultingly associated therewith.

2. In a process for separating and concentrating plutonium values from an aqueous solution thereof, the multiple carrier precipitation steps which comprise precipitating in said solution a substantially water-insoluble hydroxide, of a metal other than plutonium, which is dissolvable in an aqueous hydroxide solution, separating from the supernatant liquid the consequent metal hydroxide precipitate and the plutonium values resultingly associated therewith, dissolving the separated precipitate in an aqueous hydroxide solution, precipitating in the resulting aqueous plutonium-containing hydroxide solution a hydroxide of a metal other than plutonium by adding a source of ions of a metal whose hydroxide is insoluble in an aqueous solution of the hydroxide employed for said dissolving, and separating from the supernatant liquid the consequent metal hydroxide precipitate and the plutonium values associated therewith.

3. In a process for separating and concentrating plutonium values from an initial aqueous solution thereof, the multiple carrier precipitation steps which comprise precipitating in said solution a substantially water-insoluble hydroxide, of a metal other than plutonium, which is dissolvable in an aqueous hydroxide solution, separating from the supernatant liquid the consequent metal hydroxide precipitate and the plutonium values resultingly associated therewith, dissolving the separated precipitate in a volume of an aqueous hydroxide solution smaller than the volume of the initial plutonium solution, precipitating in the resulting aqueous plutonium-containing hydroxide solution a hydroxide of a metal other than plutonium in an amount smaller than the amount of the previous metal hydroxide precipitate by adding ions of a metal whose hydroxide is insoluble in an aqueous solution of the hydroxide employed for said dissolving, and separating from the supernatant liquids the consequent metal hydroxide precipitate and the plutonium values associated therewith.

4. In a process for separating and concentrating pluto nium values from an aqueous solution thereof, the multiple carrier precipitation steps which comprise precipitating in said solution a substantially water-insoluble hydroxide, of a metal other than plutonium, which is dissolvable in an aqueous alkali hydroxide solution, separating from the supernatant liquid the consequent metal hydroxide precipitate and the plutonium values resultingly associated therewith, dissolving the separated precipitate in an aqueous alkali hydroxide solution, precipitating in the resulting aqueous plutonium-containing hydroxide solution a hydroxide, of a metal other than plutonium, which is insoluble in aqueous alkali hydroxide but is soluble in aqueous ammonium hydroxide, by means of adding a source of the metallic cationic constituent thereof to react with the hydroxyl ions present in the solution, separating from the supernatant liquid the consequent second metal hydroxide precipitate and the plutonium values resultingly associated therewith, dissolving the separated second precipitate in aqueous ammonium hydroxide, precipitating in the resulting second aqueous plutonium-containing hydroxide solution an aqueousammonium-hydroxide-insoluble hydroxide of a metal other than plutonium by means of adding a source of the metallic cationic constituent thereof to react with the hydroxyl ions present in the solution, and separating from the supernatant liquid the consequent third metal hydroxide precipitate and the plutonium values resultingly associated therewith.

5. In a process for separating and concentrating plutonium values from an initial aqueous solution thereof, the multiple carrier precipitation steps which comprise precipitating in said initial solution a substantially waterinsoluble hydroxide, of a metal other than plutonium, which is dissolvable in an aqueous alkali hydroxide solution, separating from the supernatant liquid the consequent metal hydroxide precipitate and the plutonium values resultingly associated therewith, dissolving the separated precipitate in a volume of aqueous alkali hydroxide smaller than the volume of said initial solution, precipitating in the resulting aqueous plutonium-containing alkali hydroxide solution an aqueous-alkali-hydroxide-insoluble hydroxide, of a metal other than plutonium, which is soluble in aqueous ammonium hydroxide, by means of adding a source of the metallic cationic constituent thereof to react with the hydroxyl ions present in the solution, separating the consequent second metal hydroxide precipitate and the plutonium values resultingly associated therewith from the supernatant liquids, dissolving the separated second precipitate in a volume of aqueous ammonium hydroxide smaller than the volume of said resulting alkali hydroxide solution, precipitating in the resulting aqueous plutonium-containing ammonium hydroxide solution an aqueous-ammonium-hydroxideinsoluble hydroxide of an amphoteric metal other than plutonium by means of adding a source of the metallic cationic constituent thereof to react with the hydroxyl ions present in the solution, and separating from the supernatant liquid the consequent third metal hydroxide precipitate and the plutonium values resultingly associated therewith.

6. In a process for separating and concentrating plutonium values from an initial aqueous solution thereof, the multiple carrier precipitation steps which comprise precipitating in said initial solution a substantially waterinsoluble hydroxide, of a metal other than plutonium, which is dissolvable in aqueous ammonium hydroxide, separating from the supernatant liquid the consequent metal hydroxide precipitate and the plutonium values resultingly associated therewith, dissolving the separated precipitate in aqueous ammonium hydroxide, precipitating in the resulting aqueous plutonium-containing ammonium hydroxide solution a hydroxide, of a metal other than plutonium, which is substantially insoluble in aqueous ammonium hydroxide but is dissolvable in aqueous alkali hydroxide, by means of adding a source of the metallic cationic constituent thereof to react with the hydroxyl ions in the solution, separating from the supernatant liquid the consequent second metal hydroxide precipitate and the plutonium values resultingly associated therewith, dissolving the separated second precipitate in an aqueous alkali hydroxide solution, precipitating in the resulting second aqueous plutonium-containing hydroxide solution an aqueous-alkali-hydroxide-insoluble hydroxide of a metal other than plutonium by means of adding a source of the metallic cationic constituent thereof to react with the hydroxyl ions present in the solution, and separating from the supernatant liquid the consequent third metal hydroxide precipitate and the plutonium values resultingly associated therewith.

7. In processes for the decontamination and concentration of dissolved plutonium values, the method for separating and concentrating plutonium values from an. aqueous solution containing the same together with ferric: ions by multiple carrier precipitation which comprises: preferentially precipitating contained ferric ions as ferric ferrocyanide by adding a source of ferrocyanide ions to the solution, separating the formed ferric ferrocyanide: precipitate from the supernatant plutonium solution, pre-- cipitating in said supernatant solution, while maintaining the plutonium in said solution in the tetravalent state, a substantially water-insoluble hydroxide, of an amphoteric metal other than plutonium, which is soluble in an aqueous sodium hydroxide solution, by adding a source of the metallic cationic component thereof and adjusting the solution to an alkaline reaction, separating from the supernatant liquid the consequent amphoteric metal hydroxide precipitate and the plutonium values resultingly associated therewith, dissolving the separated hydroxide precipitate in an aqueous sodium hydroxide solution, precipitating in the resulting aqueous plutonium-containing sodium hydroxide solution a hydroxide, of a metal other than plutonium, which is substantially in soluble in aqueous sodium hydroxide but is soluble in an aqueous ammonium hydroxide, by means of adding a source of the metallic cationic constituent thereof to react with the hydroxyl ions present in the solution, separating from the supernatant liquid the consequent second metal hydroxide precipitate and the plutonium values resultingly associated therewith, dissolving the separated second hydroxide precipitate in aqueous ammonium hydroxide, precipitating in the resulting aqueous plutoniumcontaining ammonium hydroxide solution an ammoniumhydroxide-insoluble hydroxide of an amphoteric metal other than plutonium by means of adding a source of the metallic cationic constituent thereof to react with the hydroxyl ions present in the solution, and separating from the supernatant liquids the consequent amphoteric metal hydroxide precipitate and the plutonium values resultingly associated therewith.

8. In a process for separating and concentrating plutonium values from an aqueous solution thereof, the carrier precipitation steps which comprise precipitating aluminum hydroxide in said solution, and separating from the supernatant liquids the aluminum hydroxide precipitate and the plutonium values resultingly associated. therewith.

9. In a process for separating and concentrating plutonium values from an aqueous solution thereof, the carrier precipitation steps which comprise precipitating nickel. hydroxide in said solution, and separating from the super-- natant liquid the nickel hydroxide precipitate and the: plutonium values resultingly associated therewith.

10. In a process for separating and concentrating plutonium values from an aqueous solution thereof, the car rier precipitation steps which comprise precipitating; cupric hydroxide in said solution and separating from thesupernatant liquids the cupric hydroxide precipitate andr the plutonium values resultingly associated therewith.

11. In a process for separating and concentrating plu-' tonium values from an initial aqueous solution thereof, the multiple carrier precipitation steps which comprise precipitating aluminum hydroxide in said initial solution, separating from the supernatant liquid the aluminum hydroxide precipitate and the plutonium values resultingly associated therewith, dissolving the separated aluminum hydroxide precipitate in a volume of aqueous alkali hydroxide solution smaller than the volume of said initial solution, precipitating cupric hydroxide in the resulting aqueous plutonium-containing alkali hydroxide solution in an amount smaller than that of the previous aluminum hydroxide precipitate by means of adding a source of cupric ions to react with the hydroxyl ions present in the solution, and separating from the supernatant liquid the cupric hydroxide precipitate and the plutonium values resultingly associated therewith.

12. In a process for separating and concentrating plutonium values from an aqueous solution thereof, the multiple carrier precipitation steps which comprise precipitating aluminum hydroxide in said solution, separating from the supernatant liquid the aluminum hydroxide precipitate and the plutonium values resultingly associated therewith, dissolving the separated aluminum hydroxide precipitate in an aqueous alkali hydroxide solution, precipitating nickel hydroxide in the resulting aqueous plutonium-containing alkali hydroxide solution by means of adding a source of nickel ions to react with the hydroxyl ions present in the solution, and separating from the supernatant liquid the nickel hydroxide precipitate and the plutonium values resultingly associated therewith.

13. In a process for separating and concentrating plutonium values from an aqueous solution thereof, the multiple carrier precipitation steps which comprise precipitating cupric hydroxide in said solution, separating from the supernatant liquid the cupric hydroxide precipitate and the plutonium values resultingly associated therewith, dissolving the separatedcupric hydroxide precipitate in aqueous ammonium hydroxide, precipitating aluminum hydroxide in the resulting aqueous plutonium-containing ammonium hydroxide solution by means of adding a source of aluminum ions to react with the hydroxyl ions present in the solution, and separating from the supernatant liquid the aluminum hydroxide precipitate and the plutonium values resultingly associated therewith.

14. In a process for separating and concentrating plutonium values from an initial aqueous solution thereof, the multiple carrier precipitation steps which comprise precipitating aluminum hydroxide in said initial solution, separating from the supernatant liquid the aluminum hydroxide precipitate and the plutonium values resultingly associated therewith, dissolving the separated aluminum hydroxide precipitate in an aqueous alkali hydroxide solution, precipitating cupric hydroxide in the resulting aqueous plutonium-containing alkali hydroxide solution by a means of adding a source of cupric ions to react with the hydroxyl ions present in the solution, separating from the supernatant liquid the cupric hydroxide precipitate and the plutonium values resultingly associated therewith, dissolving the separated cupric hydroxide precipitate in aqueous ammonium hydroxide, precipitating aluminum hydroxide in the resulting aqueous plutonium-containing ammonium hydroxide solution by means of adding a source of aluminum ions to react with the hydroxyl ions present in the solution, and separating from the supernatant liquid the aluminum hydroxide precipitate and the plutonium values resultingly associated therewith.

15. In a process for separating and concentrating plutonium values from an aqueous solution thereof, the multiple carrier precipitation steps which comprise precipitating cupric hydroxide in said initial solution, separating from the supernatant liquid the cupric hydroxide precipitate and the plutonium values resultingly associated therewith, dissolving the separated cupric hydroxide precipitate in aqueous ammonium hydroxide, precipitating aluminum hydroxide in the resulting aqueous plutoniumcontaining ammonium hydroxide solution by means of adding a source of aluminum ions to react with the hydroxyl ions present in the solution, separating from the supernatant liquid the aluminum hydroxide precipitate and the plutonium values resultingly associated therewith, dissolving the separated aluminum hydroxide precipitate in an aqueous alkali hydroxide solution, precipitating cupric hydroxide in the resulting aqueous plutonium-containing alkali hydroxide solution by means of adding a source of cupric ions to react with the hydroxyl ions present in the solution, and separating from the supernatant liquids the consequent cupric hydroxide precipitate and the plutonium values resultingly associated therewith.

16. In a process for separating plutonium from solutions thereof the step which comprises forming an aluminum hydroxide precipitate in the solution for carrying down plutonium, separating and redissolving this precipitate to obtain a solution and forming a copper hydroxide precipitate for carrying plutonium from the last mentioned solution.

References Cited in the file of this patent Otto Hahn: Applied Radiochemistry, pages -68, Cornell University Press, Ithaca, N.Y. (1936).

- McMillan et al.: Radioactive Element 93, Physical Review, vol. 57, pages 1185-6 (1940).

Cunningham: MUC-GTS-2148, Jan. 16, 1946, declassified Nov. 22, 1957, pages (1), 2 and 38, footnote (1) Paris et al., CN-1277, page 1, Feb. 15, 1944, the latter date relied upon.

Seaborg et al.: J.A.C.S., vol. 70, pages 1128-1134, March 1948, footnote 1(b) states report submitted Mar. 21, 1942, and this date relied on. 

1. IN A PROCESS FOR SEPARATING AND CONCENTRATING PLUTONIUM VALUES FROM AN AQUEOUS SOLUTION THEREOF, THE MULTIPLE CARRIER PRECIPITATION STEPS WHICH COMPRISE PRECIPITATING IN SAID SOLUTION A HYDROXIDE OF AN AMPHOTERIC-TYPE METAL OTHER THAN PLUTONIUM, SEPARATING FROM THE SUPERNATANT, LIQUID THE CONSEQUENT METAL HYROXIDE PRECIPITATE AND THE PLUTONIUM VALUES RESULTINGLY ASSOCIATED THEREWITH, DISSOLVING THE SEPARATED PRECIPITATE TO FORM A SECOND AQUEOUS PLUTONIUM-CONTAINING SOLUTION, PRECIPITATING IN SAID SECND SOLUTION A HYDROXIDE OF A METAL OTHER THAN PLUTONIUM, AND SEPARATING FROM THE SUPERNATANT LIQUID THE CONSEQUENT METAL HYDROXIDE PRECIPITATE AND THE PLUTONIUM VALUES RESULTINGLY ASSOCIATED THEREWITH. 16 IN A PROCESS FOR SEPARATING PLUTONIUM FROM SOLUTIONS THEREOF THE STEP WHICH COMPRISES FORMING A ALUMINUM HYDROXIDE PRECIPITATE IN THE SOLUTION FOR CARRYING 